Async models, updated to [email protected] & more

For those new to this project, Wither is an ODM for MongoDB built on the official MongoDB Rust driver. This is an alpha release for 0.9.0, and is overall shaping up to be an excellent release.

A major highlight, everything is async now! This is squarely due to the mongodb team's recent 1.0 release of the driver, which supports both tokio & async-std runtimes. Wither directly reaps the benefits of these updates, so big thanks to the MongoDB team.

Lots of other good stuff here, read on to learn more.

added

• Wither is now based on the official MongoDB Rust driver.
• Everything is now async. All model methods are now async. All synchronous code has been disabled, and will be removed from the tree soon.
• Model::read_concern, Model::write_concern & Model::selection_criteria match the driver's updated mechanism for specifying these values. They may all be derived, and are always used via Model::collection and any of the model methods which interact with a model's collection.
• Added new ModelCursor type which wraps a cursor and yields model instances.

changed

• All crates cut over to edition 2018.
• Updated lots of deps. Importantly:
  • [email protected] and is now a public export of this crate.
  • [email protected] and is now a public export of this crate.
• Models are now constrained by DeserializeOwned, instead of Deserialize. This simplifies some aspects of the Model trait.
• Nearly all Model methods which interact with the collection have been updated to match the driver's new collection interface. Lots of good stuff here. Check out the docs.

index management

Index management has not yet been implemented in the mongodb driver as of 1.0, and thus the index syncing features of Model::sync have been temporarily disabled. The hope is that the mongodb team will be able to land their index management code in the driver soon, at which point we will re-enable the Model::sync functionality.

If this is important to you, please head over to wither#51 and let us know!

Notwithstanding, there are a few other changes to note:

• we have introduced the wither::IndexModel struct as a placeholder. This allows our Model interface to stay mostly the same, and allows us to preserve our index derivations using the #[derive(Model)] system.
• Model::sync is still present and callable, but has been temporarily deprecated until we are able to figure out the index management story. I mostly chose to use the deprecation pattern, even if a bit inaccurate, because it guarantees that folks will have a compiler warning letting them know that the functionality has been temporarily disabled.

wither_derive

The model derivation system has been GREATLY improved. The entire crate has been refactored. The code should be much more approachable to new folks wanting to contribute, and should be easier to maintain going forward.

• Errors are now reported via proc-macro-error and are fully spanned (which means any attribute errors related to the derive system will be highlighted with pin-point accuracy at compile time).
• We are now using dtolnay's excellent trybuild for testing the compilation of our derive system. Big win here.
• Index derivations have also been greatly simplified. Now, indexes are specified on the model-level (instead of the field-level, as they were previously).
• Indexes are derived using a keys field and an options field (which is optional). Both are expected to be quoted doc!{...} invocations. See the docs for more details.

removed

Index management :'( ... though this should only be temporary.